Nintendo8.com is a great place to play classic 8-bit Nintendo games online. Best of all the site is 100% free!
Check out Nintendo8.com for more free classic 8-bit Nintendo games. They have arranged games in the following categories: action, adventure, arcade, flight, japanese, platform, puzzle, racing, rpg, shootem up, sports, strategy, all, and a top 10 list.
You need to have the Java Runtime Environment (alt download) installed to play the games.